I have a slight oil leak somewhere on the near side rear of the engine of my '95 E320 (w124) It's above sump pan level but below head gasket level. Could be the oil filter housing but not sure where. Have tried removing starter motor to get a better look but no joy. Does anyone know where the oil pressure switch is located on this engine? I know these can sometimes leak. I have tried tightening the filter cap - it had a new O ring last filter change. Any other Ideas please?